Veteran French far-right politician Marine Le Pen shrugged off another defection from her party to rival Eric Zemmour on Sunday amid an increasingly bitter battle ahead of presidential elections in April.

One-time Le Pen ally and confidant Gilbert Collard formally announced Saturday that he was joining Zemmour's team and appeared at a rally alongside the anti-Islam writer and pundit in the south of France.

The European MP follows two other anti-immigration hardliners from Le Pen's National Rally party to join Zemmour in the last week: fellow MEP Jerome Riviere and senior party official Damien Rieu.

"I don't pay much attention to all these little manoeuvres between politicians because all of my energies are directed towards the issues of French people," Le Pen told France 3 television on Sunday.

A new poll published on Saturday showed President Emmanuel Macron winning the first round of the election on April 10 with 25 percent, followed by Le Pen and right-winger Valerie Pecresse from the Republicans party on 15.5 percent each.

The poll by the Ipsos-Sopra Steria group, with a large sample size of 12,500 people, showed Zemmour trailing in fourth place on 13 percent.

The top two candidates in the first round go through to a run-off, where Macron was seen winning against Le Pen by 57-43 percent and against Pecresse by a narrower 54-46 percent, the poll showed.

Zemmour is hoping that a string of defections this month, including by the former number two of the Republicans party, Guillaume Peltier, can help him reinvigorate a campaign that is seen by analysts as stagnating.

Speaking in Cannes on Saturday night in front of a crowd of around 4,000 people, he focused on his core issues of crime, Islam and what he sees as out-of-control immigration.

"I don't want a kebab shop in every village," he declared.

Le Pen said it was "coherent" that the defectors from her party had turned against her as she seeks to present a more moderate image to the electorate.

"Since the start of the campaign they have criticised my decision to make purchasing power my priority," she said, contrasting it with Zemmour's relentless campaigning on immigration and Islam.

"They criticise me for not wanting to get involved in the mad idea of a religious war (in France), or a civil war which they almost seem to want for the country," Le Pen added.

In a statement last week announcing his decision to join Zemmour, Rieu claimed that Le Pen's party was "no longer able to motivate our voters" and "lots of senior figures and grassroots campaigners don't believe in it any more."

But Interior Minister Gerald Darmanin told the Journal du Dimanche newspaper on Sunday that Le Pen remained "the most dangerous person for the country" as Macron's biggest rival.

"If she ever wins powers that it will lead to national division, then civil war," he warned.